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First Superconducting Transistor Created
holy_calamity writes "New Scientist reports that the first working superconducting transistor has been created, by researchers at the University of Geneva. Field effect transistors with zero electrical resistance would allow much faster operations. Only drawback is they need to be supercooled, something that may be addressed by improving the materials used."
"Only drawback is they need to be supercooled, something that may be addressed by improving the materials used." - that last part is a bit of an understatement. We're still decades (centuries?) away from room temperature superconductors.
To make laws that man cannot, and will not obey, serves to bring all law into contempt.
--E.C. Stanton
At 0.3 kelvin - just above absolute zero - these electrons flow without resistance and so create a superconductor.
So my stock fan won't quite cut it this time?
Josephson Junction has been used for switching in superconductors since I was a kid.
http://en.wikipedia.org/wiki/Josephson_effect
I'm thinking "The Blue Quench of Death", myself.
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
We have no idea how far away we are. We don't fully get it and are pretty much trying substances at random. We might figure out something that works next year or never. It's not something you can predict with any accuracy.
It is no longer uncommon to be uncommon.
As far as I know, the first superconducting transistor was reported in 2006:
cond-mat/0601434
Speed isn't only determined by on-state resistance. Capacitance & inductance matter too and will be the limiting factors for a theoretical transistor that's 0 resistance on and infinite resistance off. Such a theoretical transistor won't dissipate heat, so it won't get hot. However, heat will be dissipated somewhere else because current still must flow from high potential to low potential. Furthermore, transition times aren't arbitrarily fast, and during the transition, the transistor will dissipate resistive power; this could be a big problem for systems cooled below 4 K.
"Only drawback is they need to be supercooled, something that may be addressed by improving the materials used." - that last part is a bit of an understatement.
Is an understatement from the New Sensationalist (as it should properly be called) an oxymoron?
The New Sensationalist runs a story every couple of weeks about how some new breakthrough will revolutionize something or other in the next two years. Has anyone gone through their predictions like we do with psychics to see what their actual hit rate really is?
Prime numbers are exactly what Alan Greenspan says they are -S. Minsky
We'd love to get our hands on some superconducting FETs. The ones I'm designing around right now have 5 milliohms Rds, and they're *still* getting so hot we have to solder big heat sinks onto the backsides of them.
But this just shifts the problem to the gate drive, because during any finite time period between 'off' and 'on' the FET acts like a big power resistor and heats up. Even if people ever make these so they're superconducting at room temp, they'll still heat up when in the active region. (Or we'd need to develop drivers that could produce instantaneous off/on transition times.) So we'd need ones that could remain superconductive in well over room-temp transients. If you have a superconducting FET that suddenly stops superconducting because of a temperature peak, it'll vaporize just about instantaneously. These would be an exciting gamble.
Nostalgia's not what it used to be.
Yes, you can insulate a device, so that in almost all cases (definitely in the case of a fast-switching transistor) the main heat source is the device itself.
Here's a commercial box that cools a 2-inch wafer of high-temperature superconductor to around 80K. This box uses 80 watts including whatever other signal processing stuff is in there.
Another source (Cryogenics 42 (2002) 705-718) says that 1W of cooling power at 4K will cost you 5kW of input power using a straightforward helium compressor. This scales as 1/temperature^2 for higher temperatures, but for lower temperatures you'd switch to a different type of refrigerator.
0.3K refrigerators using helium 3 would not use more than 10kW, but this is already too much for most applications.
So the practical significance of this research is that it may be reproduced with higher temperature materials, not that we will build THz DSPs at 0.3K.
Use of the term "supercooled" in this context is bogus. Something is supercooled if it remains a liquid, even though it should be a solid at those conditions (or it remains a gas where it should be a liquid). If you put a glass of very clean distilled water in a freezer you'll find out that you can cool it down to -7*C or lower without freezing. It will momentarily freeze if you drop a snow flake into it though, or when you hit the glass with a screwdriver.
(For the curious: this is because extremely small crystals and droplets have higher free enthalpy than the bulk phase due to surface effects, so their formation is inhibited.)
This has nothing to do with superconductors, because they are always solids and cannot be supercooled. For superconductors you're looking for "cooled below its critical temperature", but I admit that it doesn't sound as good as "supercooled".
Those who would give up liberty to obtain working drivers, deserve neither liberty nor working drivers.
Think of power converters. Think of a broadcast TV transmitter.